qicharts2: Quality Improvement Charts

Functions for making run charts, Shewhart control charts and
Pareto charts for continuous quality improvement. Included control charts are:
I, MR, Xbar, S, T, C, U, U', P, P', and G charts. Non-random variation in the
form of minor to moderate persistent shifts in data over time is identified by
the Anhoej rules for unusually long runs and unusually few crossing
[Anhoej, Olesen (2014) <doi:10.1371/journal.pone.0113825>].
Non-random variation in the form of larger, possibly transient, shifts is
identified by Shewhart's 3-sigma rule [Mohammed, Worthington, Woodall (2008)
<doi:10.1136/qshc.2004.012047>].